From coal-mining waste to construction material: a study of its mineral phases

Abstract

The study from the recycling of coal mining waste from NW of Spain as pozzolans materials in cement industry is the scope of this present study. The thermal activation of coal-mining wastes, the formation of their hydrated phases and their evolution are analyzed, over pozzolanic reactions at 1, 7 and 28 days following activation. The coal-mining waste showed good pozzolanic activity, following thermal activation at 600 and 900 °C for 2 h. Total destruction of kaolinite is produced after treatment at 600 °C/2 h retention in the oven. This temperature and time are best suited for activation of the best environmental way. The compounds arising during the pozzolanic reaction in coal-mining waste activated at 600° and 900° in a Ca(OH)2 system were C–S–H gels, stratlingite (C2ASH8), tetracalcium aluminate hydrate (C4AH13), layered double hydroxides and monosulfoaluminate. When the temperature is 600 °C appeared layered double hydroxides via the metastable phase is favored during the first 7 days of reaction, while stratlingite is present as the major crystalline phase at 28 days into the pozzolanic reaction.

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Acknowledgments

This research has been supported by the Spanish Ministry of Economy and Competitiveness (Project Ref. MAT2012-37005-CO3-01/02/03). The authors are also grateful to the Sociedad Anónima Hullera Vasco-Leonesa and to Spanish Cement Institute (IECA) for their help in this research.